feat: customizable placeholder strings as metadata_field option

src/print_text.rs

@@ -1,5 +1,5 @@
 //! This file deals with formatting and outputting to stdout.
-use log::{error, info};
+use log::error;
 use std::collections::HashMap;
 use string_builder::Builder;
 
@@ -85,12 +85,25 @@ fn append_prefix(b: &mut Builder, data: &Data) {
 /// data: Data struct containing the field-text HashMap.
 fn append_fields(b: &mut Builder, cfg: &Config, data: &Data) {
     let mut idx = 0;
-    let len = data.field_text.len() as i32;
 
     for field in &cfg.metadata_fields {
-        if let Some(string) = data.field_text.get(&field.field) {
+        // setup (string, fmt) to contain placeholder or data, if extant.
+        let f = data.field_text.get(&field.field);
+        let (string, fmt) = if f.is_some() {
+            (f.unwrap(), &field.format)
+        } else if field.placeholder.len() != 0 {
+            (&field.field, &field.placeholder)
+        } else {
+            continue;
+        };
+
+        // insert separator in front of non-empty non-first field.
+        if idx > 0 {
+            b.append(cfg.metadata_separator.as_str())
+        };
         idx += 1;
 
+        // FIXME: extract to its' own function.
         if cfg.escape_chars {
             let s: &String = &string
                 .chars()
@@ -100,15 +113,9 @@ fn append_fields(b: &mut Builder, cfg: &Config, data: &Data) {
                 })
                 .collect();
 
-                b.append(field.format.replace("{}", s.as_str()));
+            b.append(fmt.replace("{}", s.as_str()));
         } else {
-                b.append(field.format.replace("{}", string.as_str()));
+            b.append(fmt.replace("{}", string));
-            }
-            if idx < len {
-                b.append(cfg.metadata_separator.as_str())
-            };
-        } else {
-            info!("failed to get {} value!", field.field);
         }
     }
 }

src/structs/config.rs

@@ -12,6 +12,8 @@ pub struct Field {
     pub num_chars: u32,
     /// Formatting to apply. (the value "{}" is substituted with the actual string)
     pub format: String,
+    /// Placeholder string to insert when the field is empty. (the value "{}" is substituted with the actual string).
+    pub placeholder: String,
 }
 
 impl Field {
@@ -20,14 +22,16 @@ impl Field {
     /// field: name of the field
     /// num_chars: maximum length of the field
     /// format: what formatting to apply to the field
+    /// placeholder: the placeholder string to use
     ///
     /// returns:
     /// a new Field with the given parameters.
-    fn new(field: String, num_chars: u32, format: String) -> Self {
+    fn new(field: String, num_chars: u32, format: String, placeholder: String) -> Self {
         Field {
             field,
             num_chars,
             format,
+            placeholder,
         }
     }
 
@@ -36,15 +40,29 @@ impl Field {
     /// field: name of the field
     /// num_chars: maximum length of the field
     /// format: (optional), formatting to apply.
+    /// placeholder: (optional), what placeholder to use.
     ///
     /// returns:
     /// a new Field with the given parameters.
-    pub fn constructor(field: &str, num_chars: u32, format: Option<String>) -> Self {
+    pub fn constructor(
-        if let Some(format) = format {
+        field: &str,
-            Self::new(field.to_owned(), num_chars, format)
+        num_chars: u32,
+        format: Option<String>,
+        placeholder: Option<String>,
+    ) -> Self {
+        let fmt = if format.is_some() {
+            format.unwrap()
         } else {
-            Self::new(field.to_owned(), num_chars, "{}".to_owned())
+            "{}".to_owned()
-        }
+        };
+
+        let place = if placeholder.is_some() {
+            placeholder.unwrap()
+        } else {
+            "No {}".to_owned()
+        };
+
+        Self::new(field.to_owned(), num_chars, fmt, place)
     }
 }
 
@@ -241,8 +259,8 @@ impl Config {
     /// It contains the "title" and "artist" fields, with 40 and 20 maximum characters respectively.
     fn default_metadata_fields() -> Vec<Field> {
         vec![
-            Field::constructor("xesam:title", 40, None),
+            Field::constructor("xesam:title", 40, None, None),
-            Field::constructor("xesam:artist", 20, None),
+            Field::constructor("xesam:artist", 20, None, None),
         ]
     }
 

src/update_message.rs

@@ -109,19 +109,14 @@ pub fn update_message(cfg: &Config, data: &mut Data, ratings: &Vec<String>) {
                                 key,
                                 value_to_string(value, cfg.array_separator)
                             );
-                            data.field_text
-                                .insert(key.to_owned(), value_to_string(value, cfg.array_separator))
-                        }
-                        None => {
-                            trace!("update_messages: field {} has no value!", key);
-                            if field.field.eq("bs:isFavorite") {
-                                data.field_text.remove(key);
-                                continue;
-                            }
                             data.field_text.insert(
                                 key.to_owned(),
-                                format!("No {}", key.trim_start_matches("xesam:")),
+                                value_to_string(value, cfg.array_separator),
-                            )
+                            );
+                        }
+                        None => {
+                            trace!("update_messages: field {} has no value", key);
+                            data.field_text.remove(key);
                         }
                     };
                 }